We just got our decision email on the 5th, and the package is said to arrive on the 11th. I agree, they should just tell you in the email! As if this process isn't drawn out long enough as it is! 
They used to tell you the decision in the email - when settlement visas were processed in NYC (they moved to Sheffield in March 2013), they sent out either an 'approval' or 'refusal' email. However, Sheffield just send out a generic 'decision made' email.
I don't want to get too excited, what if the visa is denied? Although, it seems most people who receive a "decision made" email, get a visa in the mail. Has anyone heard otherwise?
Everyone receives the 'decision made' email, whether their visa has been approved or refused. However, approximately 95-98% of settlement visas applications made in the US are approved, so most people will get their visa.
If it is refused, then you need to see what the reasons for refusal are and if it is possible for you to meet the reasons for refusal, you can re-apply for the visa, addressing those reasons. If you are refused for a reason that can't be fixed (i.e. you don't and can't meet the financial requirement), then you won't be able to re-apply.
They may offer you the chance to appeal the decision if it is refused, but appeals will only be successful if you met all the requirements but UKVI made a mistake in refusing the visa. Appeals can take about a year to be processed, so usually it's not worth bothering with them.
